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Discussion

It is never too early to speculate about the weather around here for the upcoming winter and there are some very interesting possible early clues about the prospects. To begin with, when dealing with long-range possibilities, it is generally best to start with a look at the oceans as they have a much higher heat capacity than the atmosphere, and the biggest ocean by far is the Pacific Ocean. A transition is now occurring in the tropical Pacific with respect to sea surface temperatures from La Nina (colder than normal) to El Nino (warmer than normal) and it appears that the upcoming winter will likely feature a “weak-to-moderate” El Nino in that region. This could play a role in the precipitation amounts around here this winter as El Nino patterns tend to produce active sub-tropical jets which, in turn, often lead to enhanced storminess along the Mid-Atlantic coast.

As far as temperatures are concerned, I have been monitoring the evolution of two different long-range forecast models including NOAAs “Climate Forecast System” and the Japanese Meteorological Agency “JAMSTEC” model. Quite interestingly, both of these models are hinting at the prospects of a substantial reversal in temperatures for much of the US during the autumn from above to below normal, and this change to below normal is then predicted by these models to persist into the upcoming winter months.

By combining both the possible El Nino in the tropical Pacific with the below normal model temperature forecasts, one can see the scenario for a colder and stormy winter in the Mid-Atlantic, but it is still very early and the devil is in the details. For example, the prediction of a "weak-to-moderate" El Nino is not necessarily sufficient by itself in determining potential Mid-Atlantic winter weather conditions as experience has shown that its location in the tropical Pacific Ocean is often as critical as its magnitude (ie will it be an eastern-based El Nino or more centrally-based?). Also, another wild card for the upcoming winter lies with the atmospheric pressure patterns over the north Atlantic Ocean which are quite hard to forecast well in advance, and they often have an influence on wintertime temperatures in the Mid-Atlantic region. Stay tuned as we continue to monitor the ever evolving oceanic and atmospheric patterns over the next several months.